266: "The OBIX object model illustrated below in Figure [x]. It consists of a common base Object (o:obj) and is built of 12 child objects. This section describes the structure of these elements and their attributes ("Facets").
422: The language "All objects support the concept of null. Null is the absence of value" is opaque. Not sure what to suggest as a replacement.

445: Remove first sentence.

453: Add normative reference to PNG

Section 4.18.9 (520-538)
Avoid redefining common internet specification. Reference http://www.iana.org/time-zones . Use RFC6557 as a guide on how to discuss this.

Section 4.18.10. It would be helpful to reference the SI Units document when the term "SI Units" is forst used. http://physics.nist.gov/cuu/Units/units.html Add as a normative reference.